The present invention relates to a portable support platform or construction base suitable for use with model train layouts, model race car tracks, doll houses, miniature villages, architectural models and the like. Through the use of corrugated paperboard elements or similar lightweight materials, a rigid, torsion-resisting planar structural unit is achieved having great strength and extremely light weight. A plurality of the structural units may be connected with one another to define a base of a desired size and configuration.